Going Wild

One of the questions I get asked most often is how to take a bread recipe and substitute sourdough starter for baker’s yeast.

The short answer, in my humble opinion, is: you can’t. Do I hear gasps? Can Ms. Wild Yeast be advising against using wild yeast?

No, she isn’t. But let’s think about this a minute. You have a recipe you like, and it uses baker’s yeast. (You do like the recipe, don’t you? Otherwise why would you want to keep it around?) Now you want to simply take out the the baker’s yeast and replace it with wild yeast. Simple, right?

But with sourdough starter, you’re not only adding yeast, your’re adding flour, water, bacteria and the acids they produce (these are what make sourdough sour), alcohol, and other compounds that are products of fermentation. And in so doing, you’re potentially going to be changing (for better or worse) some things: dough consistency and strength, fermentation time, keeping quality, and, of course, flavor and texture of the bread, to name a few.

So, what was it you liked about that original recipe, anyway? If you care to, you can read more of my thoughts on tweaking recipes. It pretty much boils down to this: if you do things differently, you may well wind up with a different result.

That said, I don’t want to make it sound like you can’t or shouldn’t use a baker’s yeast recipe as a starting place to develop a different, sourdough-leavened, bread. What I can tell you is where I would start If I were going to do this (and I have, plenty of times). What I can’t give you is a pat formula — and that would be boring anyway, wouldn’t it?

I’m assuming that you use a scale, know the hydration of your starter, and are starting with a recipe that gives ingredients in grams. (If you don’t, I’m very sorry but I’m probably not your best bet.) I’ll also assume your original recipe is a “straight dough;” that is, it does not contain a preferment such as a poolish or sponge; I can talk about those in another post if anyone is interested.

I start by thinking about how much prefermented flour I would like to have in my dough. In other words, how much flour will be contributed by the starter I will add? Typically this is between 15 and 25%, although for rye and whole-grain breads it is often higher. I think a good place to start is 15% (which is, by the way, the percentage of prefermented flour in Norwich Sourdough). If you don’t like the result you can change it on the next batch.

Now look at the original formula. Let’s say it is

500 g flour

325 g water

5 g yeast

10 g salt

15% of the 500 grams of flour is 75 grams. So I need to know how much of my starter contains 75 grams of flour.

I keep a 100%-hydration starter, so the calculation is easy. In a 100%-hydration starter, there are equal amounts of flour and water, by weight. Therefore, to get 75 grams of flour, I need 150 grams of starter, which brings along with it 75 grams of water. If your starter has a different hydration, you will need to do a little more math.

Now, since I’m adding 75 grams each of flour and water, I reduce the flour and water in the final dough by those amounts. This maintains, in the final dough, the same ingredients as in the original recipe, minus the yeast. My adjusted formula becomes

425 g flour

250 g water

150 g 100%-hydration sourdough starter

10 g salt

These numbers are the easy part, and remember they are just a starting point. Some things to keep in mind:

The dough may actually need less (or maybe more) water than its baker’s yeast counterpart. (I hold back a small amount of water to make adjustments in the mixing process, don’t you?)

The dough will almost surely need a longer fermentation time than the original recipe.

Sour flavor increases with a larger amount of starter in the formula and with longer fermentation times. But fermentation time decreases as the amount of starter goes up. In my experience, increasing the amount of starter has a greater impact on sourness than increasing fermentation time.

A higher dough temperature also decreases fermentation time. Depending on whom you talk to, a higher temperature may increase or decrease the sourness of the bread. Have fun with that.

The acidity of sourdough makes the dough stronger, with the effect increasing as fermentation time increases. You may need to mix the dough a little less initially.

Think of this as an iterative process to get to the result you want, and do what works for you!

Overall, I find using LESS starter gives more of a sour taste. It gives the bacteria longer to work.

If you use a fresh and healthy starter, which I always recommend, you aren’t adding sour with the starter like you’d add chocolate taste by adding chocolate chips, but the organisms that will create the sour taste.

If you check out Dr. Wood’s first book, he has a recipe for a San Francisco sourdough bread he makes 4 ways. One has 4 cups of starter and is risen in about an hour (if memory serves), the next has one or two cups of starter and is risen in 4 to 6 hours, the last has 1/4 cup of starter and takes about 16 hours to rise. The hydration of all the doughs is the same.

The last one, with 1/4 cup of starter, is MUCH more sour than the first two.

Great post – as usual. I have been experimenting with adding a starter that is at various stages of maturity, and using various techniques to grow the starter (time temperature, hydration, etc.) I have found the condition of my starter (maturity, how it was grown) has more impact on the final loaf then the amount of starter used.

BTW – I read your link to the old post “On Tweaking”. After thinking about it I realized it was second nature for me to wait until tasting the final product and then decide if I had been cooking in “Mode 1” or “Mode 2”. Now that I’m aware of this I know my conscience will force me to mentally “declare” mode 1 or mode 2 in advance. Thanks for the nightmares. :~)

Wow. I was under the impression that nearly any bread recipe could be “adapted” for sourdough, and your explanation is wonderfully thorough and makes perfect sense. You are a good teacher for those of us that are still new to sourdough. This post was fun to read.

Good to know. Sometimes we tend to think we can make all these substitutions at will – but I learned from an ol’ boyfriend who was an Executive Chef that baking is chemistry. Change one item and everything changes.

(He wasn’t such a hot boyfriend – but I learned a lot about food and cooking that year. My husband now is the beneficiary of all that learning.)

I would love to hear what you have to say about substituting wild yeast in commercial-yeast recipes with pre-ferments. So many of my favorite bread recipes use a biga or a poolish and I’m itching to try them out with my starter, so if you have any tips or considerations, I’d love to hear them before I waste a bunch of time and flour!

I am new to this and enjoying making rye sourdough at the moment
Your blog has answered many questions in my mind, thank you
I don’t know who you are,what is your name?
I am facinated by the science of it all which you clearly understand. This knowledge enables one to be flexible and experiment
Having said that the process is so simple
Do you have a book on the subject and what is the title
I look forward to trying out more things

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[…] Substituting Sourdough Starter for Baker’s Yeast | Wild YeastNov 8, 2010 … One of the questions I get asked most often is how to take a bread recipe and substitute sourdough starter for baker’s yeast. The short answer … […]

[…] Adding starter to your recipe adds flour and water as well as yeast so the balance in your recipe may have been altered. The above formula gives a starter that is at 100% hydration (equal quantity of flour and liquid by weight) so, if you add 100g of starter, you will have added 50g of water and 50g of flour to the recipe in addition to the yeast. For a thorough rundown on how to convert a recipe, please see the Wild Yeast Blog. […]

[…] Adding starter to your recipe adds flour and water as well as yeast so the balance in your recipe may have been altered. The above formula gives a starter that is at 100% hydration (equal quantity of flour and liquid by weight) so, if you add 100g of starter, you will have added 50g of water and 50g of flour to the recipe in addition to the yeast. For a thorough rundown on how to convert a recipe, please see the Wild Yeast Blog. […]

[…] a sourdough starter if you want to, though it may take some experimentation. The Wild Yeast Blog has a great guide on how to do exactly that. You can also make amazingly delicious sourdough pancakes, pizza crust […]

[…] a sourdough starter if you want to, though it may take some experimentation. The Wild Yeast Blog has a great guide on how to do exactly that. You can also make amazingly delicious sourdough pancakes, pizza crust […]

[…] into a stand mixer bowl NOTE: I used 1 cup of my sourdough starter, so I followed the instructions here to substitute for some of the flour and water in the ingredients list above. My starter is 100% […]